Mattock breaking the wrong block

Verified against the spelunky.ai port v0.1.10 on 28 October 2026.

The Mattock digs: its swing breaks a block ahead of the player, at his height or, if there's none there, ahead of his feet. Which block it breaks isn't always the one it tested for. Depending on where he stands, it can break the floor under him, so he drops through, or skip the block ahead and break the next.

Facing left, the player swings a Mattock at the floor ahead of him: it breaks the block beyond that one, and the block in front stays. He steps right and swings again: this time it breaks the block he stands on, and he drops into the hole ^[1].

The Mattock's hit sits 16 pixels ahead of the player, at his height ^[2]. When its animation ends, it tests the point at its position for a block, then the point 9 pixels below, ahead of his feet, and breaks the block instance_place finds there ^[3]:

hit = false;
if (collision_point(x, y, oSolid, 0, 0))
{
    obj = instance_place(x, y, oSolid);
    if (not obj.invincible) hit = true;
}
else if (collision_point(x, y+9, oSolid, 0, 0))
{
    obj = instance_place(x, y+9, oSolid);
    if (not obj.invincible) hit = true;
}

collision_point tests one point, but instance_place tests the hit's whole sprite box there, and returns the first block in the level's order that overlaps it. The box is 11 pixels wide, so where the player stands it can overlap two blocks: facing right with his position at 0 to 7 pixels into a block, the block under him as well as the one ahead; facing left at 0 to 2, the block beyond the one ahead. When that other block comes first, it breaks instead ^[4]. A custom level makes its blocks row by row from the left, so there, facing right, half of all positions dig the player's own floor ^[4].

Dig with the Mattock along a floor, facing right, standing near the left edge of a block. The replay of the clip's staged scene, on a custom level, pins both cases: facing left, the swing breaks the block beyond the one ahead; facing right, the block under the player, and he falls in ^[5].

The spelunky.ai port reproduces it exactly: it's in docs/quirks.md's list of the 1.1 source's bugs ^[4], and the oracle's fingerprint of the replay pins the blocks broken. No option turns it off.